Ship Launching: Airbag Launching
Ceremonial ship launching involves the performance of ceremonies associated with the process of transferring a vessel to the water. It is a nautical tradition in many cultures, dating back thousands of years, to accompany the physical process with ceremonies which have been observed as public celebration and a solemn blessing, usually but not always, in association with the launch itself.
Ship launching imposes stresses on the ship not met during normal operation and, in addition to the size and weight of the vessel, represents a considerable engineering challenge as well as a public spectacle.
Airbag launching
Based on the ship shapes, the ship may be launched, using air bags, by either end launching type (video) or side launching type.
Airbag launching refers to a method to launch vessels with marine air bags. It is a methodology for ship launching utilizing air bags.
The Xiao Qinghe shipyard launched a tank barge with marine airbags on January 20, 1981 and it is known as the first use of marine airbags.
This kind of ship launching method has the advantages of requiring less permanent infrastructure, risk, and cost. The airbags provide support to the hull of the ship, air bags rolling motion take a vessel launch into water, thus it is arguably safer than other options like sideways launching.
Unlike most other launching methods that are fixed infrastructures, airbag launching has relatively less limitations and can be used in versatile ways. It overcomes the disadvantage of fixed track launching in which capacity of shipbuilding and ship repairing is limited by the fixed infrastructures especially in small and medium-sized shipyards.
There are three ways to arrange air bags when using the end launching type
A. Linear arrangement
B. Staggered arrangement
C. Two-lines arrangement
Airbag
Airbag structure
Marine air bags consist of three parts:
– Air bag body: the main, cylindrical part of the air bag after being fully inflated with compressed air.
– Air bag heads: conical parts connecting the body and the mouths of the air bag.
– Air bag mouths: either metal valves mounted on both ends of the air bag for inflating with air or a valve on one end and a metal lug on the other end used to haul the air bag.
Air bag size and model
The diameter of an air bag varies; sizes include 0.8 m, 1.0 m, 1.2 m, 1.5 m, 1.8 m, etc.
The length of an air bag is specified by the customer when it is manufactured.
Towing arrangement
A windlass shall be used to control the movement of the ship. Tow system that comprises windlass, steel wire rope and pulley set shall be securely fastened to the ground anchor in front of the berth.
In general, a slow windlass shall be selected for ship launching. The veering speed of the windlass shall be 9 m/min to 13 m/min.
The forces of the windlass and the steel wire rope should be calculated carefully by technicians of ship yards or air bags company.
